Ill. Const. art. X, § 3

Neither the General Assembly nor any county, city, town, township, school district, or other public corporation, shall ever make any appropriation or pay from any public fund whatever, anything in aid of any church or sectarian purpose, or to help support or sustain any school, academy, seminary, college, university, or other literary or scientific institution, controlled by any church or sectarian denomination whatever; nor shall any grant or donation of land, money, or other personal property ever be made by the State, or any such public corporation, to any church, or for any sectarian purpose. (Source: Illinois Constitution.)